TULSA, Okla. — The Sierra Club filed a lawsuit in Washington, D.C., District Court against the U.S. Environmental Protection Agency on Wednesday, seeking to ensure that the federal agency enforces a state plan that monitors and reduces pollution from Oklahoma coal-fired power plants.

The Sierra Club warned the EPA in February that the lawsuit was coming in 60 days if the agency failed to act, the environmental group said in a statement.

No action was taken, so the Sierra Club followed through, said Whitney Pearson, associate field organizer for group’s Oklahoma chapter.

“Sierra Club brought this citizen suit because EPA must act to either approve or disapprove the state’s plan to address these excess harmful emissions,” Pearson said. “What we ultimately expect out of this action is to end the free pass that large polluters currently have which allows them to emit unlimited amounts of pollution during certain phases of their operations. Because people need to breathe all the time, limits of the amount of pollution that polluters can emit need to apply all the time. This case is one step in getting to that point.”

The EPA will review the details of the Sierra Club lawsuit, said Dave Bary, EPA Region 6 spokesman.

“EPA will discuss with the Sierra Club and the state of Oklahoma the next appropriate steps in this legal matter,” Bary said.

The plants involved include the Oklahoma Gas and Electric Co.’s Muskogee plant, Pearson said. OG&E has another coal-fired power plant, Sooner Station, in Red Rock.

Brian Alford, OG&E spokesman, said the company will have to wait for an outcome.

“So, once we know what this process will be, rest assured we will follow that process, once we know what that is,” Alford said.

All coal plants in Oklahoma emit excess emissions, Pearson said.

“And we are reminding the EPA to help close this loophole so that Oklahomans can breathe cleaner air,” Pearson said.

The coal-fired plants are allowed to pollute above legal levels, said Jenna Garland, associate press secretary with the Sierra Club Southeast and South Central Region.

“Currently, under what is known as a pollution excuse provision, coal plants can turn off pollution controls when starting up, shutting down, or performing maintenance on a malfunctioning plant,” she said.

The loophole allows Oklahoma plants to pump more mercury and smog into the air than in other places around the country, Garland said.

“Although the Clean Air Act requires the EPA to approve or disapprove Oklahoma’s proposed plan to manage these emissions, EPA failed to act by the deadline,” she said.

Coal-fired plants release excess emissions during periods of starting, shutting down and maintenance because operators generally turn off any existing pollution controls during these times, which cause significant emissions spikes to occur, Garland said.

“For example, starting up a coal boiler that has not been running can take hours to bring it up to temperature, and during this time no pollution controls are running on the boiler, so 100 percent of the pollution is going into our air,” she said.

Additionally, engineers at regulatory agencies do not include these excess emissions in a plant’s air permit, Garland said. As a result, they exceed the amount allowed by permit.